Metal piping is preferred in high pressure systems. The problem with metal piping is that it is prone to rust or corrode. Therefore today high pressure systems are increasingly being made out of plastic. The plastic pipes are do not corrode and the reduced weight of the plastic piping facilitates installation. However connections between plastic pipes, especially where they are attached to metal piping as proven problematic. Failures often occur at threaded connections between metal and plastic pieces. One reason for this is that threaded plastic cannot take high torques or stresses. Plastic adapter threads are prone to attack by solvent adhesives used to secure plastic and metal parts together. During installation cracks in plastic couplings often occur from overtightening.